1. Field of the Invention
The invention relates to a yarn brake with two preferably disc-shaped or plate-shaped brake elements pressed resiliently against one another by magnetic loading.
2. Discussion of the Relevant Art
Yarn brakes of this type are used to a great extent for imparting yarn tension to running yarns on textile machines and are known, for example, from EP 499 218 A2, DE-A 20 00 268, DE-C 864 073, GB-A 850,858 or DE 43 01 507 A1.
These publications propose a yarn brake, in which the brake plates are induced to clamp or brake the yarn by means of opposite-pole magnetic rings. The braking force may be exerted in each case via a permanently magnetic ring which is arranged on the brake plate and which is fixed relative to the brake plate via a thread. The forces of attraction of opposite-pole permanent magnets depend on the distance between the two permanently magnetic rings, there being an approximately square relation between the magnitude of the force of attraction and the distance. The braking force may thereby be set appropriately for the particular purpose. However, the disadvantage of this arrangement and design of brake plates having opposite-pole magnetic rings is that it is not properly possible to operate the yarn brake independently of position, and that sensitive adjustability of the braking force from zero up to the full locking of the brake is made difficult.
Furthermore, the older application DE 44 09 450 A1 disclosed a generic yarn brake, in which additional axially polarized magnets are provided on the bearing shaft in order to assist the centring of the brake plates. The magnets are polarized in such a way that they axially repell the brake plate located in front of them in each case. At least one of the additional magnets is arranged axially adjustably on the bearing shaft.
The yarn brakes known from the prior art described above have in common the fact that relatively complicated solutions are provided in order to allow self-cleaning and, at the same time, sufficient fine adjustment of the braking force to achieve a high degree of operating reliability.